Solve 4x + 12 = 84
The solution of 4x + 12 = 84 is x = 18.
How to work it out
- 1
The goal is to get x alone. Undo the operations in the opposite order: first the addition, then the multiplication.
- 2
Subtract 12 from both sides:
- 3
Divide both sides by 4:
- 4
Check: put x = 18 back into the equation.
LaTeX source of the formulas on this page
\[ 4x + 12 = 84\ \Rightarrow\ x = 18 \]
\[ 4x + 12 = 84 \]
\[ 4x + 12 - 12 = 84 - 12 \ \Rightarrow\ 4x = 72 \]
\[ \frac{4x}{4} = \frac{72}{4} \ \Rightarrow\ x = 18 \]
\[ 4\cdot18 + 12 = 72 + 12 = 84 \checkmark \]Trying values of x in 4x + 12 = 84
| x | 4x + 12 | Equals 84? |
|---|---|---|
| 16 | 76 | no |
| 17 | 80 | no |
| 18 | 84 | yes |
| 19 | 88 | no |
| 20 | 92 | no |
Questions
What is x in 4x + 12 = 84?
The solution of 4x + 12 = 84 is x = 18.
How do you solve 4x + 12 = 84?
Subtract 12 from both sides to get 4x = 72, then divide both sides by 4 to get x = 18.
How do I check the answer?
Replace x by 18: 4(18) + 12 = 84, which is 84.